USB will not allow me to delete files

This is not a “Trash is full empty the trash first” answer. When I try to move a file to the trash, I get an error message " The Item xxxxx can’t be moved to the trash because it can’t be deleted".  I have 2 Sandisk Cruzer Glide usb’s that give this error message.  This message shows up whether I try to move an entire folder or an single file to the trash. I have a MAC desktop.  Help would be greatly appreciated. Thank you.